The Arduino SD library said “Card type: SDHC” but “Could not find FAT16/FAT32 partition.” The problem was, as someone found in the SparkFun forums, that the card communication couldn’t keep up. In the CardInfo example sketch I switched SPI_HALF_SPEED to SPI_QUARTER_SPEED and that fixed it. Hope this helps someone else having the same problem!

My setup was Arduino Uno => jumpers to breadboard => Logic Level Converter => jumpers to elsewhere on breadboard => SD card breakout; it sounds like once the connection is more direct the problem may go away.

On a Mac with Arduino 1.0.5, note that SoftwareSerial is inside Ardiuno.app ( /Applications/Arduino.app/Contents/Resources/Java/libraries/SoftwareSerial/SoftwareSerial.h ) and the constant is just _SS_MAX_RX_BUFF . (NewSoftSerial is no longer required with Arduino 1+.) I ended up setting it to 256, since a GGA + RMC sentence is about 140 characters.

but it never started producing position data / blinking the red LED. SparkFun support advised me to send a FULL_COLD_RESTART:

Serial.println("$PMTK104*37"); // FULL COLD RESTART

Details are in https://www.sparkfun.com/datasheets/GPS/Modules/PMTK_Protocol.pdf . This resets the GPS’s almanac, which very rarely comes with bad data or something. Note that unlike the example code where the GPS’s 3.3v output can be fed into a 5v Arduino (I was using an Uno), to send data to the GPS you’ll have to have a 3.3v Arduino or a logic level converter (like BOB-12009 ).

Also, TinyGPS only uses GGA and RMC sentences, so I configured my unit to only send those, and only once every 5 fixes (that is, 1Hz):

I think the response is shorter (< 10ms). I drove a laser with tone() and pointed it at a photoresistor*, and (via ascii-art graph from analogRead()) can clearly see a 200Hz signal, implying < 2.5ms until a detectable response. Note however that at 32Hz the rise and falloff are much more visible; clearly at 200Hz the photoresistor (or some part of the system) doesn’t fully stabilize. However at 32Hz, that’s still ~15ms response time.

I used these to illuminate paper Minecraft avatars, as indicators for when players are logged in to my server. The diffuse housing and bright LEDs illuminate the (1" cube heads of the) avatars nicely, even in bright indoor light. I can run 5 at full brightness (with the recommended 150Ω/330Ω resistors) without a problem from a USB-powered Teensy’s digital out pins.

I had a 5v source and wanted to make sure I wouldn’t damage the NM / draw too much current if I left it on, so I overcompensated with a 4.7 ohm resistor. If I do my arithmetic right (having measured 5.2 ohms for the NM), that leaves only 2.6v for the NM, which may contribute to its slightly slow response, as compared to Miga’s demo video lifting a fishing weight.

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